U.S. patent application number 14/413323 was filed with the patent office on 2015-07-09 for micromirror array, manufacturing method for micromirror array, and optical elements used in micromirror array.
This patent application is currently assigned to NITTO DENKO CORPORATION. The applicant listed for this patent is NITTO DENKO CORPORATION. Invention is credited to Noriyuki Juni.
Application Number | 20150192709 14/413323 |
Document ID | / |
Family ID | 49915992 |
Filed Date | 2015-07-09 |
United States Patent
Application |
20150192709 |
Kind Code |
A1 |
Juni; Noriyuki |
July 9, 2015 |
MICROMIRROR ARRAY, MANUFACTURING METHOD FOR MICROMIRROR ARRAY, AND
OPTICAL ELEMENTS USED IN MICROMIRROR ARRAY
Abstract
A manufacturing method for a micromirror array includes:
preparing transparent flat substrates; attaching each of the
substrates at a predetermined position of a machining stage of a
dicing machine; sequentially forming parallel linear grooves
arranged at intervals in one surface of each substrate; and
stacking the substrates together so that the directions in which
the linear grooves of the respective substrates extend are
orthogonal to each other as seen in plan view. The substrates are
stacked together in a manner selected from the group consisting of:
the front surface of one of the substrates and the back surface of
the other substrate are joined together for the stacking of the
substrates; the front surfaces of the respective substrates are
joined together for the stacking of the substrates; and the back
surfaces of the respective substrates are joined together for the
stacking of the substrates.
Inventors: |
Juni; Noriyuki;
(Ibaraki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NITTO DENKO CORPORATION |
Ibaraki-shi, Osaka |
|
JP |
|
|
Assignee: |
NITTO DENKO CORPORATION
Ibaraki-shi, Osaka
JP
|
Family ID: |
49915992 |
Appl. No.: |
14/413323 |
Filed: |
July 8, 2013 |
PCT Filed: |
July 8, 2013 |
PCT NO: |
PCT/JP2013/068581 |
371 Date: |
January 7, 2015 |
Current U.S.
Class: |
359/627 ;
29/428 |
Current CPC
Class: |
G02B 5/045 20130101;
G02B 5/09 20130101; B29D 11/00596 20130101; G02B 5/124 20130101;
G02B 5/08 20130101; Y10T 29/49826 20150115; G02B 5/0816
20130101 |
International
Class: |
G02B 5/08 20060101
G02B005/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 13, 2012 |
JP |
2012-157827 |
Jun 27, 2013 |
JP |
2013-134994 |
Claims
1. A micromirror array comprising: two optical elements each having
a plurality of parallel linear grooves arranged at predetermined
spacings and formed in a first surface of a transparent flat
substrate, the two optical elements being stacked together so that
the directions in which the linear grooves of the respective
optical elements extend are orthogonal to each other as seen in
plan view, to thereby constitute a single unit, wherein the two
optical elements are stacked together in a manner selected from the
group consisting of: (A) a manner in which the front surface of one
of the optical elements where the linear grooves are formed and the
back surface of the other optical element where the grooves are not
formed are brought into abutment with each other; (B) a manner in
which the front surfaces of the respective optical elements where
the linear grooves are formed are brought into abutment with each
other; and (C) a manner in which the back surfaces of the
respective optical elements where the grooves are not formed are
brought into abutment with each other, wherein the micromirror
array is capable of forming a mirror image of an object to be
projected which is disposed on a first surface side of the
micromirror array at a spatial position on a second surface side
thereof symmetrical to the object with respect to the plane of an
element surface of the micromirror array.
2. A micromirror array comprising: a plurality of parallel linear
grooves arranged at predetermined spacings and formed in a first
surface of a transparent flat substrate constituting an optical
element and in a second surface thereof opposite from the first
surface, wherein the directions in which the linear grooves on the
front surface side and the linear grooves on the back surface side
extend are orthogonal to each other as seen in plan view, wherein
the micromirror array is capable of forming a mirror image of an
object to be projected which is disposed on a first surface side of
the micromirror array at a spatial position on a second surface
side thereof symmetrical to the object with respect to the plane of
an element surface of the micromirror array.
3. A method of manufacturing a micromirror array, comprising:
preparing a transparent flat substrate; attaching the substrate at
a predetermined position of a machining stage of a dicing machine;
sequentially forming a plurality of parallel linear grooves
arranged at predetermined intervals in a surface of said substrate
by using a rotary blade; and stacking two substrates where said
linear grooves are formed together so that the directions in which
the linear grooves of the respective substrates extend are
orthogonal to each other as seen in plan view, to thereby
constitute a single unit, wherein the two substrates are stacked
together in a manner selected from the group consisting of: (D) a
manner in which the front surface of one of the substrates where
the linear grooves are formed and the back surface of the other
substrate where the grooves are not formed are joined together for
the stacking of the substrates; (E) a manner in which the front
surfaces of the respective substrates where the linear grooves are
formed are joined together for the stacking of the substrates; and
(F) a manner in which the back surfaces of the respective
substrates where the grooves are not formed are joined together for
the stacking of the substrates.
4. A method of manufacturing a micromirror array, comprising:
preparing a transparent flat substrate; attaching the substrate at
a predetermined position of a machining stage of a dicing machine;
sequentially forming a plurality of parallel linear grooves
arranged at predetermined intervals in a first surface of said
substrate by using a rotary blade; removing the substrate once from
said machining stage to flip the substrate upside down and to
thereafter attaching the substrate again at a predetermined
position of the machining stage; and sequentially forming a
plurality of parallel linear grooves similar to those in said first
surface and arranged at predetermined intervals in a second surface
of said substrate by using a rotary blade, so as to extend in a
direction orthogonal to the linear grooves in said first surface as
seen in plan view.
5. An optical element for a micromirror array, comprising: a
transparent flat substrate comprising a plurality of parallel
linear grooves arranged at predetermined spacings formed in a
surface thereof.
6. The optical element for a micromirror array according to claim
5, wherein a "height-to-width" ratio of a width of substrate front
surface portions lying between adjacent linear grooves to a height
of the substrate front surface portions from the bottom of the
grooves is not less than 3.0.
7. A micromirror array comprising: two optical elements as recited
in claim 6 stacked one on top of the other, wherein the micromirror
array is capable of forming a mirror image of an object to be
projected which is disposed on a first surface side of the
micromirror array at a spatial position on a second surface side
thereof symmetrical to the object with respect to the plane of an
element surface of the micromirror array.
Description
TECHNICAL FIELD
[0001] The present invention relates to a micromirror array which
forms a mirror image of an object to be projected in space, a
method of manufacturing the same, and optical elements for use in
the micromirror array.
BACKGROUND ART
[0002] A micromirror array in which multiple "unit optical elements
each reflecting light by means of one or more mirror surfaces" are
disposed on a substrate (base) constituting an element surface of
an optical element has been developed as an image-forming optical
element which image-forms a three-dimensional or two-dimensional
object, image and the like. In particular, a micromirror array
including a large number of recessed unit optical elements or
protruding unit optical elements arranged in an array and each
having "two mirror surfaces orthogonal to each other" (a corner
reflector) disposed at right angles or at an angle close to the
right angles to this substrate has received attention in recent
years because it is relatively simple in structure and it is
expected to reduce manufacturing costs (with reference to Patent
Literature 1).
[0003] Examples of the aforementioned micromirror array are shown
in FIGS. 12 and 13.
[0004] In a recessed type micromirror array 50 (hereinafter
referred to simply as an "array" in some cases) shown in FIG. 12, a
large number of minute holes 51 in the shape of a quadrangular tube
(unit optical elements; the ratio of length, width and depth is
approximately 1:1:1 in this example) are formed in one surface of a
flat substrate 3 (element surface P) made of a transparent material
so as to extend to the other surface thereof, and are arranged in a
checkerboard pattern angled at 45 degrees with respect to an
observer. At least two surfaces out of the four side surfaces
(inner wall surfaces) of each of the unit optical elements (minute
holes 51) are formed as mirror surfaces (light-reflective wall
surfaces).
[0005] In a protruding type micromirror array 60 shown in FIG. 13,
a large number of transparent minute protruding portions 61 in the
shape of a quadrangular prism (unit optical elements; cubes having
an approximately 1:1:1 ratio of width, depth and height in this
example) are formed on one surface of a substrate 4 (element
surface P) made of a transparent material, and are arranged in a
checkerboard pattern angled at 45 degrees with respect to an
observer. In the case of the aforementioned array 60, at least two
surfaces out of the four side surfaces (wall surfaces) of each of
the unit optical elements (minute protruding portions 61) are
formed as mirror surfaces (light-reflective wall surfaces).
[0006] As shown in FIG. 14, when light incident on one surface
(front or back) side of a micromirror array L of the aforementioned
recessed type, protruding type or the like passes through the array
L, this light (dash-double-dot lines) is reflected once from each
of the two mirror surfaces on opposite sides of one corner K of
each of the unit optical elements (twice in total). The light
reflected twice (passing light) forms a mirror image (reversed
image M' indicated by a chain line) of an object M to be projected
at a spatial position on the other surface side of each
aforementioned array L (position symmetrical to the object M with
respect to the plane of the element surface P).
[0007] An example of a method of producing a recessed type
micromirror array as mentioned above which has hitherto been
employed includes a method of reversely transferring the shape of
the aforementioned unit optical elements by a nano imprint
technique or an electroforming technique through the use of a metal
mold (molding die) configured such that a large number of minute
protruding portions complementary in shape to the recessed unit
optical elements, respectively, are previously formed on a flat
foundation (Patent Literature 1). An example of a method of
producing a protruding type micromirror array which has been
proposed includes a method of forming a large number of minute
prisms arranged at predetermined spacings on a substrate by
injection molding or hot press molding through the use of a metal
mold (stamper) having a large number of minute cavities (recessed
portions) complementary in shape to the protruding unit optical
elements (Patent Literature 2).
CITATION LIST
Patent Literature
[0008] PTL 1: International Publication No. WO2007/116639 [0009]
PTL 2: Japanese Published Patent Application No. 2011-191404
SUMMARY OF INVENTION
[0010] Unfortunately, the methods of manufacturing the micromirror
arrays using the aforementioned molding die and the stamper involve
the need for a mold release (mold removal) step after the molding.
The presence of such a mold release step not only makes the
manufacturing procedure complicated but also is prone to cause a
problem such that a sharp image cannot be obtained because the
finished unit optical elements adhere to the aforementioned molding
die and the like and partly come off or become chipped during the
mold release to result in defects caused in the arrays. Thus, a
configuration of a micromirror array as an alternative to these and
a new manufacturing method which does not use the molding die have
been sought.
[0011] In view of the foregoing, it is therefore an object of the
present invention to provide a micromirror array capable of forming
a bright high-luminance image, optical elements for use in the
micromirror array, and a method of manufacturing a micromirror
array which is capable of manufacturing an array at low costs
without a mold release or mold removal process.
[0012] To accomplish the aforementioned object, a first aspect of
the present invention is intended for a micromirror array for
forming a mirror image of an object to be projected which is
disposed on a first surface side of a flat optical element at a
spatial position on a second surface side thereof symmetrical to
the object with respect to the plane of an element surface of this
optical element, the micromirror array being characterized in that
two optical elements each having a plurality of parallel linear
grooves arranged at predetermined spacings and formed in a first
surface of a transparent flat substrate by dicing using a rotary
blade are stacked together so that the directions in which the
linear grooves of the respective optical elements extend are
orthogonal to each other as seen in plan view, to thereby
constitute a single unit, the two optical elements being stacked
together in a manner selected from the group consisting of: (A) a
manner in which the front surface of one of the optical elements
where the linear grooves are formed and the back surface of the
other optical element where the grooves are not formed are brought
into abutment with each other; (B) a manner in which the front
surfaces of the respective optical elements where the linear
grooves are formed are brought into abutment with each other; and
(C) a manner in which the back surfaces of the respective optical
elements where the grooves are not formed are brought into abutment
with each other.
[0013] A second aspect of the present invention is intended for a
micromirror array for forming a mirror image of an object to be
projected which is disposed on a first surface side of a flat
optical element at a spatial position on a second surface side
thereof symmetrical to the object with respect to the plane of an
element surface of this optical element, the micromirror array
being characterized in that a plurality of parallel linear grooves
arranged at predetermined spacings are formed in a first surface of
a transparent flat substrate constituting said optical element and
in a second surface thereof opposite from the first surface by
dicing using a rotary blade so that the directions in which the
linear grooves on the front surface side and the linear grooves on
the back surface side extend are orthogonal to each other as seen
in plan view.
[0014] To accomplish the same object, a third aspect of the present
invention is intended for a method of manufacturing a micromirror
array as recited in the first aspect, the method comprising the
steps of: preparing a transparent flat substrate; attaching the
substrate at a predetermined position of a machining stage of a
dicing machine; sequentially forming parallel linear grooves
arranged at predetermined intervals in a surface of said substrate
by using a rotary blade; and stacking two substrates where said
linear grooves are formed together so that the directions in which
the linear grooves of the respective substrates extend are
orthogonal to each other as seen in plan view, to thereby
constitute a single unit, the two substrates being stacked together
in a manner selected from the group consisting of: (D) a manner in
which the front surface of one of the substrates where the linear
grooves are formed and the back surface of the other substrate
where the grooves are not formed are joined together for the
stacking of the substrates; (E) a manner in which the front
surfaces of the respective substrates where the linear grooves are
formed are joined together for the stacking of the substrates; and
(F) a manner in which the back surfaces of the respective
substrates where the grooves are not formed are joined together for
the stacking of the substrates.
[0015] Further, a fourth aspect of the present invention is
intended for a method of manufacturing a micromirror array as
recited in the second aspect, the method comprising the steps of:
preparing a transparent flat substrate; attaching the substrate at
a predetermined position of a machining stage of a dicing machine;
sequentially forming parallel linear grooves arranged at
predetermined intervals in a first surface of said substrate by
using a rotary blade; removing the substrate once from said
machining stage to flip the substrate upside down and to thereafter
attaching the substrate again at a predetermined position of the
machining stage; and sequentially forming parallel linear grooves
similar to those in said first surface and arranged at
predetermined intervals in a second surface of said substrate by
using a rotary blade so as to extend in a direction orthogonal to
the linear grooves in said first surface as seen in plan view.
[0016] Also, a fifth aspect of the present invention is intended
for an optical element for a micromirror array, wherein a plurality
of parallel linear grooves arranged at predetermined spacings are
formed in a surface of a transparent flat substrate. A sixth aspect
of the present invention is intended for a micromirror array
including two such optical elements stacked one on top of the
other.
[0017] The present inventor has broken the bounds of common
technical practice such that a molding method using the
aforementioned conventional metal mold, stamper and the like is
used as a machining method for enhancing the efficiency of the
manufacture of the micromirror array, and has considered and
carried out the use of dicing which achieves precise groove
engraving. As a result, the present inventor has succeeded in
obtaining a micromirror array capable of forming a bright sharp
image at lower costs and in higher yields than conventional
manufacturing methods.
[0018] In the micromirror array according to the first aspect of
the present invention as described above, the linear grooves in the
substrate are formed by dicing using the rotary blade. For this
reason, the wall surfaces (side surfaces) on opposite sides
constituting each of the grooves are in the form of
light-reflective vertical surfaces (mirror surfaces, i.e. first
mirror surfaces constituting corner reflectors to be described
later). The plurality of linear grooves are parallel to each other
and are disposed at predetermined spacings in one substrate. One
substrate which is rotated 90 degrees horizontally is stacked on
top of the other substrate in any one of the aforementioned manners
(A) to (C), to thereby constitute a single unit. With this
configuration, a group of linear grooves on one substrate side and
a group of linear grooves on the other substrate side are
orthogonal to each other in the form of a lattice, as seen in plan
view in the direction of the front and back of the substrates
(vertical direction). A multiplicity of "corner reflectors" each
comprised of two vertically spaced mirror surfaces are formed at
the intersections of these groups of grooves. These corner
reflectors cause light incident on one surface side of the
aforementioned substrate (optical element) to be reflected once
from each of the two mirror surfaces constituting each corner
reflector, and then cause the reflected light to be transmitted
through the substrate to the other side thereof. Thus, the
micromirror array according to the first aspect of the present
invention is capable of brightly and sharply forming a mirror image
of an object to be projected which is disposed on one surface side
of the aforementioned substrate at a spatial position on the other
surface side symmetrical to the object with respect to the plane of
the substrate.
[0019] In the micromirror array according to the second aspect of
the present invention, a group of linear grooves formed in the
first surface (front surface) of one substrate and a group of
linear grooves formed in the second surface (back surface) thereof
opposite from the first surface are orthogonal to each other in the
form of a lattice, as seen in plan view in the direction of the
front and back of the substrate (vertical direction). A
multiplicity of "corner reflectors" each comprised of two
vertically spaced mirror surfaces as in the micromirror array of
the aforementioned first aspect are formed at the intersections of
these groups of grooves. Also in this micromirror array, light
incident on one surface side of the aforementioned substrate
(optical element) is reflected once from each of the two mirror
surfaces constituting each corner reflector, and then the reflected
light is transmitted through the substrate to the other side
thereof. Thus, the micromirror array according to the second aspect
of the present invention is capable of brightly and sharply forming
a mirror image of an object to be projected which is disposed on
one surface side of the aforementioned substrate at a spatial
position on the other surface side symmetrical to the object with
respect to the plane of the substrate.
[0020] Next, the manufacturing method for a micromirror array
according to the third aspect of the present invention includes the
step of stacking these substrates together in any one of the
aforementioned manners (D) to (F) to thereby constitute a single
unit after forming the linear grooves in each substrate which
constitute the aforementioned corner reflectors by dicing using the
rotary blade. Thus, the aforementioned manufacturing method for a
micromirror array is capable of accurately and efficiently forming
the optical elements having the aforementioned linear grooves and
the micromirror array, and is capable of manufacturing the
micromirror array easily at low costs as compared with conventional
manufacturing methods. Further, the aforementioned manufacturing
method for a micromirror array does not include any step which is
prone to damage the array, such as mold release (mold removal).
This improves the yield in the manufacture of the array and the
optical elements constituting the array. Moreover, the groove
formation using the aforementioned dicing makes it relatively easy
to adjust the optical performance of the optical elements, such as
the increase in the aspect ratio [the ratio of height (length in
the thickness direction of the substrates) H to width (width in the
horizontal direction of the substrates) W] of the light reflecting
surfaces (mirror surfaces) by changing the intervals (spacings)
between the grooves and the depth of the grooves. This is
advantageous in that the flexibility of array design is
improved.
[0021] In the manufacturing method for a micromirror array
according to the fourth aspect of the present invention, the linear
grooves on the first surface (front surface) side of the substrate
and the linear grooves on the second surface (back surface) side
thereof opposite from the first surface side which constitute the
aforementioned corner reflectors are also formed by dicing using
the rotary blade. For this reason, the method is capable of
accurately and efficiently forming the linear grooves. Like the
manufacturing method for a micromirror array according to the third
aspect, the manufacturing method for a micromirror array according
to the fourth aspect is thus capable of manufacturing the
micromirror array easily at low costs as compared with conventional
manufacturing methods. Further, the aforementioned manufacturing
method for a micromirror array according to the fourth aspect does
not include any step which is prone to damage the array, such as
mold release (mold removal). This improves the yield in the
manufacture of the array and the optical element constituting the
array. Similarly, this method is capable of relatively easily
adjusting the optical performance of the optical element, such as
changing the intervals (spacings) between the grooves and the depth
thereof.
[0022] In the optical element (optical element unit) for use in the
aforementioned micromirror array, the plurality of parallel linear
grooves arranged at predetermined spacings are formed in one
surface of the transparent flat substrate. In particular, the
optical element wherein the ratio "height H/width W" between the
width (W) of the substrate front surface portions lying between
adjacent ones of the linear grooves and the height (H) of the
substrate front surface portions from the bottom of the grooves
(the aforementioned aspect ratio) is not less than 3.0 is
preferably used. Also, the micromirror array including two optical
elements as described above stacked one on top of the other is
capable of more brightly and more sharply forming the mirror image
of the object to be projected at the spatial position on the second
surface side thereof symmetrical to the object with respect to the
plane of the substrate.
BRIEF DESCRIPTION OF DRAWINGS
[0023] FIG. 1 is a perspective view showing a structure of a
micromirror array according to a first embodiment of the present
invention.
[0024] FIG. 2 is an exploded perspective view of the micromirror
array according to the first embodiment of the present
invention.
[0025] FIG. 3 is a perspective view showing a structure of a
micromirror array according to a second embodiment of the present
invention.
[0026] FIG. 4 is an exploded perspective view of the micromirror
array according to the second embodiment of the present
invention.
[0027] FIG. 5 is a perspective view showing a structure of a
micromirror array according to a third embodiment of the present
invention.
[0028] FIG. 6 is an exploded perspective view of the micromirror
array according to the third embodiment of the present
invention.
[0029] FIG. 7 is a perspective view showing a structure of a
micromirror array according to a fourth embodiment of the present
invention.
[0030] FIG. 8A is a plan view of corner reflector portions inside
the micromirror array according to the present invention as seen in
a vertical direction, and FIG. 8B is a schematic view showing a
three-dimensional structure of one corner reflector (a pair of
mirror surfaces of one corner reflector) thereof.
[0031] FIG. 9 is a schematic view of the configuration of a dicing
machine for use in a method of manufacturing a micromirror array
according to the embodiments of the present invention.
[0032] FIG. 10 is a schematic view illustrating a method for an
experiment in projecting a mirror image according to the
embodiments of the present invention.
[0033] FIG. 11 shows reference photographs taken with a camera and
showing how a spatial image (character) looks like according to the
embodiments of the present invention.
[0034] FIG. 12 is a schematic view showing a structure of a
conventional recessed type micromirror array on an enlarged
scale.
[0035] FIG. 13 is a schematic view showing a structure of a
conventional protruding type micromirror array on an enlarged
scale.
[0036] FIG. 14 is a schematic view illustrating a manner of image
formation of a mirror image by means of a micromirror array.
DESCRIPTION OF EMBODIMENTS
[0037] Next, embodiments according to the present invention will
now be described in detail with reference to the drawings.
[0038] FIG. 1 is a perspective view showing a structure of a
micromirror array according to a first embodiment of the present
invention. FIG. 2 is an exploded perspective view of this
micromirror array. Linear grooves 1g and 1'g provided in substrates
1 and 1' are drawn on an enlarged scale for easier understanding of
the structure thereof (the same applies to the subsequent figures).
In the following description, a surface in which the grooves 1g and
1'g are formed is referred to as a "front surface" side 1a and 1'a,
a surface in which the grooves 1g and 1'g are not formed is
referred to as a "back surface" side 1b and 1'b, and a flat area of
each substrate to which the engraving of the grooves 1g and 1'g
does not extend is referred to as a plate-like portion 1c and
1'c.
[0039] The micromirror array 10 according to the first embodiment
of the present invention shown in FIG. 1 is formed as an
"image-forming optical element" for forming a mirror image of an
object to be projected which is disposed on one surface side (front
surface 10a side or back surface 10b side) of the array 10 at a
spatial position on the other surface side (back surface 10b side
or front surface 10a side) symmetrical to the object with respect
to the plane of an element surface P of this array 10. As shown in
FIG. 2, the optical elements (substrates 1 and 1') constituting
this micromirror array 10 are configured such that a plurality of
parallel linear grooves 1g and grooves 1'g spaced at predetermined
intervals are formed in the upper front surfaces 1a and 1'a of the
transparent flat substrates 1 and 1', respectively, by dicing using
a rotary blade J to be described later. The aforementioned
micromirror array 10 is formed using the two optical elements
(substrates 1 and 1') identical with each other in shape. With the
first upper substrate 1' rotated relative to the second lower
substrate 1 so that the continuous directions in which the grooves
1g and the grooves 1'g provided in the substrates 1 and 1' extend
are orthogonal to each other as seen in plan view, the back surface
1'b (plate-like portion 1'c) where the grooves 1'g are not formed
in the upper substrate 1' is brought into abutment with the front
surface 1a where the grooves 1g are formed in the lower substrate
1. These substrates 1 and 1' are stacked one on top of the other to
constitute the single array. This is a characteristic of the
micromirror array 10 according to the first embodiment of the
present invention.
[0040] The configuration of the aforementioned micromirror array 10
will be described in further detail. The substrates 1 and 1'
(substrates prior to the formation of the grooves 1g and 1'g)
constituting the respective optical elements are base bodies for
engraving of the aforementioned grooves 1g and 1'g, and are made of
a material having a visible light transmittance of not less than
80%, such as glass and acrylic resin, for example. These substrates
1 and 1' are generally in the form of hard plates having a fixed
thickness (thickness on the order of 0.5 to 10.0 mm). The upper
surfaces (front surfaces 1a and 1' a) of the substrates 1 and 1'
are engraved with the aforementioned linear grooves 1g and 1'g by
dicing. Substrate surface portions which lie between adjacent ones
of the aforementioned linear grooves 1g and which are not engraved
with the grooves are protruding portions (ridge portions or ridge
areas) protruding toward one surface of the substrate 1 by the
formation of the adjacent grooves. The flat areas (plate-like
portions 1c and 1'c) to which the engraving of the grooves 1g and
1'g does not extend are support bases for the aforementioned ridge
portions formed unengraved between the grooves 1g and 1'g.
[0041] The grooves 1g and 1'g in the aforementioned substrates 1
and 1' are formed using a rotary blade (with reference to the
dicing blade J in FIG. 9 and the like) of a dicing machine, and are
spaced at predetermined intervals (spacings) in one direction in
surfaces to be machined (front surfaces) of the substrates 1 and 1'
so as to be parallel to each other. It should be noted that the
side surfaces (wall surfaces) constituting these grooves 1g and
1'g, which are formed by dicing using the aforementioned rotary
blade, are formed as light-reflective vertical surfaces (mirror
surfaces). The term "vertical surfaces" as used in the present
invention shall be meant to include not only surfaces exactly
perpendicular to the substrate bottom surface (or groove bottom
surface) but also surfaces the standing angle of which with respect
to the substrate bottom surface is slightly (for example, about 2
degrees or less) deviated, and may be substantially the same in
light-reflective properties.
[0042] Depending on the thickness of the aforementioned blade J
(total thickness between end surfaces), the grooves 1g and 1'g
obtained by engraving using the dicing blade J have a groove width
G of approximately 20 to 350 .mu.m and a groove depth H of
approximately 50 to 500 .mu.m, when the blade J having a thickness
of the order of 0.015 mm (15 .mu.m) to 0.3 mm (300 .mu.m) is in
general used. The remaining regions (ridge portions) where these
grooves 1g and 1'g are not formed are in the form of parallel ribs
having a width W of approximately 50 to 300 .mu.m and a height H of
approximately 50 to 500 .mu.m (the same as the depth of the
grooves).
[0043] With the first upper substrate 1' rotated 90 degrees
horizontally relative to the second lower substrate 1 (that is,
with a phase difference of 90 degrees between the lower substrate 1
and the upper substrate 1') as shown in FIG. 2, the back surface
1'b of the upper substrate 1' (the lower surface of the plate-like
portion 1'c) is brought into abutment with the front surface 1a
(upper surface) of the lower substrate 1. The two substrates 1 and
1' in which the aforementioned respective linear grooves 1g and 1'g
are formed are stacked together to constitute the single (integral)
micromirror array 10 as shown in FIG. 1 [aforementioned manner
(A)]. At this time, there is a phase difference of 90 degrees
between the lower substrate 1 and the upper substrate 1' as
mentioned above. Thus, the directions (continuous directions) in
which the grooves 1g and 1'g of the respective substrates 1 and 1'
formed in the same shape extend are disposed in orthogonal relation
to each other as seen in plan view [three-dimensionally in "skew"
relation; with reference to FIG. 8B].
[0044] When the aforementioned micromirror array 10 is seen in the
direction of the front and back of the substrates (vertical
direction) in this state [with reference to FIG. 8A], the grooves
1'g of the upper substrate 1' and the grooves 1g of the lower
substrate 1 are orthogonal to each other in the form of a lattice
as seen in plan view. A corner reflector [a pair of vertically
spaced surfaces of a corner reflector; FIG. 8B] is formed at the
intersection of each of the grooves 1'g and each of the grooves 1g.
Such a corner reflector includes a light-reflective vertical
surface (mirror surface K2) of each of the grooves 1'g of the upper
substrate 1', and a light-reflective vertical surface (mirror
surface K1) of each of the grooves 1g of the lower substrate 1.
[0045] Because of the aforementioned configuration of the
aforementioned micromirror array 10, light incident on one surface
side of the aforementioned array 10 is reflected once from the
light-reflective vertical surface (mirror surface) of each of the
grooves 1'g of the upper substrate 1', and is reflected once from
the light-reflective vertical surface (mirror surface) of each of
the grooves 1g of the upper substrate 1. Then, the reflected light
is transmitted through the array 10 to the other side thereof.
Thus, the micromirror array 10 according to the present first
embodiment is capable of forming a mirror image of an object to be
projected which is disposed on one surface side of the array 10 at
a spatial position on the other surface side symmetrical to the
object with respect to the plane of the array 10, as shown in FIG.
14.
[0046] The light-reflective vertical surfaces (vertically spaced
mirror surfaces K1 and K2) constituting the corner reflectors
formed when the substrates 1 and 1' are stacked together have an
apparent virtual aspect ratio [the ratio of height H (length in the
thickness direction of the substrates) to width W (width of ridge
portions in the horizontal direction of the substrates)=H/W; with
reference to FIG. 8B] greater than that of conventional products.
Therefore, these mirror surfaces reflect more light to project a
bright and sharp mirror image ("FIG. 8" and the "virtual aspect
ratio" will be described in detail later).
[0047] It should be noted that the optical elements (optical
element units) constituting the aforementioned micromirror array
may be produced by methods other than dicing using the rotary blade
as mentioned earlier. It is however desirable that dicing using the
rotary blade is used for the efficient production of optical
elements having a high aspect ratio (height H/width W of not less
than 3.0).
[0048] It is also preferable that the two, upper and lower, optical
elements constituting the aforementioned micromirror array are
identical in specification and are stacked together in
front-to-back or back-to-front relation when in use. However, when
the decrease in light reflection efficiency is not taken into
consideration, optical elements which are different in
specification (different in shape), e.g. different in groove width,
in spacings and in ridge portion height, may be stacked together
when in use.
[0049] Next, a second embodiment of the present invention will be
described.
[0050] FIG. 3 is a perspective view showing a structure of a
micromirror array according to the second embodiment of the present
invention. FIG. 4 is an exploded perspective view of this
micromirror array.
[0051] The micromirror array 20 according to the second embodiment
of the present invention shown in FIG. 3 is also formed as an
"image-forming optical element" for forming a mirror image of an
object to be projected which is disposed on one surface side (front
surface 20a side or back surface 20b side) of the array 20 at a
spatial position on the other surface side (back surface 20b side
or front surface 20a side) symmetrical to the object with respect
to the plane of the element surface P of this array 20. As in the
aforementioned first embodiment, the optical elements constituting
this micromirror array 20 are also configured such that the
plurality of parallel linear grooves 1g and grooves 1'g spaced at
predetermined intervals are formed in the front surfaces 1a and 1'a
of the transparent flat substrates 1 and 1', respectively, by
dicing using the rotary blade J to be described later. The
structure of the optical elements (substrates 1 and 1'), which is
similar to that of the substrates 1 and 1' used in the first
embodiment, will not be described in detail.
[0052] The micromirror array 20 according to the second embodiment
differs from the micromirror array 10 according to the first
embodiment in that the first upper substrate 1' is flipped upside
down so that the front surface 1' a in which the grooves 1'g are
formed is positioned to face downward when in use, as shown in FIG.
4. Specifically, the aforementioned micromirror array 20 is formed
using the two optical elements (substrates 1 and 1') identical with
each other in shape. With the first upper substrate 1' flipped
upside down and rotated 90 degrees relative to the second lower
substrate 1, the front surface 1'a where the grooves 1'g are formed
in the upper substrate 1' is brought into abutment with the front
surface 1a where the grooves 1g are formed in the lower substrate
1, as shown in FIG. 4. These substrates 1 and 1' are stacked one on
top of the other so that the directions in which the grooves 1g and
the grooves 1'g provided in the substrates 1 and 1' extend are
orthogonal to each other as seen in plan view, to constitute the
single array 20, as shown in FIG. 3 [aforementioned manner (B)].
This is a characteristic of the micromirror array 20 according to
the second embodiment of the present invention.
[0053] According to the aforementioned configuration, there is a
phase difference of 90 degrees between the lower substrate 1 and
the upper substrate 1'. Thus, as shown in FIG. 3, the directions in
which the grooves 1g and 1'g of the respective substrates 1 and 1'
formed in the same shape extend are disposed in orthogonal relation
to each other as seen in plan view [three-dimensionally in "skew"
relation; FIG. 8B]. Thus, when the aforementioned micromirror array
20 is seen in the direction of the front and back of the substrates
(vertical direction), the grooves 1'g of the upper substrate 1' and
the grooves 1g of the lower substrate 1 are orthogonal to each
other in the form of a lattice as seen in plan view. A corner
reflector is formed at the intersection of each of the grooves 1'g
and each of the grooves 1g. Such a corner reflector includes a
light-reflective vertical surface (mirror surface) of each of the
grooves 1'g of the upper substrate 1', and a light-reflective
vertical surface (mirror surface) of each of the grooves 1g of the
lower substrate 1 [FIG. 8A].
[0054] In the micromirror array 20 according to the second
embodiment, light incident on one surface side of the
aforementioned array 20 is hence reflected once from the
light-reflective vertical surface (mirror surface) of each of the
grooves 1'g of the upper substrate 1', and is reflected once from
the light-reflective vertical surface (mirror surface) of each of
the grooves 1g of the upper substrate 1. Then, the reflected light
is transmitted through the array 20 to the other side thereof.
Thus, the micromirror array 20 according to the present second
embodiment is also capable of forming a mirror image of an object
to be projected which is disposed on one surface side of the array
20 at a spatial position on the other surface side symmetrical to
the object with respect to the plane of the array 20, as shown in
FIG. 14. Also, the light-reflective vertical surfaces (mirror
surfaces) constituting the aforementioned corner reflectors have a
great aspect ratio [apparent virtual aspect ratio; H/W; FIG. 8B].
Therefore, as in the aforementioned first embodiment, these
light-reflective vertical surfaces (mirror surfaces) are capable of
projecting a bright and sharp mirror image, as compared with
conventional products.
[0055] In the micromirror array 20 according to the aforementioned
second embodiment, the optical elements (substrates 1 and 1') may
be stacked one on top of the other, with the positions of the
optical elements exchanged (in reverse order). FIG. 5 is a
perspective view showing a structure of a micromirror array 30
formed in such a manner according to a third embodiment. FIG. 6 is
an exploded perspective view of the aforementioned micromirror
array 30.
[0056] As shown in FIGS. 5 and 6, the micromirror array 30
according to the third embodiment is formed using the two optical
elements identical with each other in shape. With the first lower
substrate 1' flipped upside down and rotated 90 degrees relative to
the second upper substrate 1, the back surface 1b of the upper
substrate 1 (the lower surface of the plate-like portion 1c) is
brought into abutment with the back surface 1'b of the lower
substrate 1' (the upper surface of the plate-like portion 1'c).
These substrates 1 and 1' are stacked one on top of the other so
that the directions in which the grooves 1g and the grooves 1'g
provided in the substrates 1 and 1' extend are orthogonal to each
other as seen in plan view, to constitute the single array 30
[aforementioned manner (C)].
[0057] According to the configuration of the micromirror array 30
according to the aforementioned third embodiment, the grooves 1g
and 1'g of the substrates 1 and 1' are arranged so that the
directions in which the grooves extend are orthogonal to each other
in the form of a lattice as seen in plan view. A corner reflector
[FIG. 8A] is formed at the intersection of each of the grooves 1'g
and each of the grooves 1g. Such a corner reflector includes a
light-reflective vertical surface (mirror surface) of each of the
grooves 1g of the upper substrate 1, and a light-reflective
vertical surface (mirror surface) of each of the grooves 1'g of the
lower substrate 1'. This produces effects similar to those of the
aforementioned micromirror array 20. The third embodiment is
similar to the aforementioned first and second embodiments in being
capable of increasing the aspect ratio [apparent virtual aspect
ratio; H/W; FIG. 8B] of the light-reflective vertical surfaces
(mirror surfaces) of the aforementioned corner reflectors.
[0058] Next, a fourth embodiment according to the present invention
will be described.
[0059] FIG. 7 is a perspective view showing a structure of a
micromirror array according to a fourth embodiment of the present
invention.
[0060] The micromirror array 40 according to the fourth embodiment
of the present invention shown in FIG. 7 is also formed as an
"image-forming optical element" for forming a mirror image of an
object to be projected which is disposed on one surface side (front
surface 40a side or back surface 40b side) of the array 40 at a
spatial position on the other surface side (back surface 40b side
or front surface 40a side) symmetrical to the object with respect
to the plane of the element surface P of this array 40. While the
micromirror arrays 10 to 30 of the aforementioned first to third
embodiments are formed using the two substrates 1 and 1' each
provided with the linear grooves 1g and 1'g formed in one surface
thereof, the micromirror array 40 according to the fourth
embodiment is formed using a single substrate 2 (optical
element).
[0061] Specifically, as shown in FIG. 7, the aforementioned
micromirror array 40 (optical element) is configured such that a
plurality of parallel linear grooves 2g and grooves 2g' spaced at
predetermined intervals are formed in an upper front surface 2a and
a lower back surface 2b, respectively, of the transparent flat
substrate 2 by dicing using the rotary blade J to be described
later. The grooves 2g on the front surface 2a side and the grooves
2g' on the back surface 2b side are arranged so that the directions
(continuous directions) in which the grooves extend are orthogonal
to each other as seen in plan view. This is a characteristic of the
micromirror array 40 according to the fourth embodiment of the
present invention.
[0062] Like the aforementioned substrate 1, the substrate
(substrate prior to the formation of the grooves 2g and 2g')
constituting the aforementioned micromirror array 40 (optical
element) is a base body for engraving of the linear grooves 2g and
2'g, and is made of a material (optical element material) having a
visible light transmittance of not less than 80%, such as glass and
acrylic resin, for example. This substrate 2 is generally in the
form of a hard plate having a fixed thickness (thickness on the
order of 0.5 to 10.0 mm). The upper and lower surfaces (front and
back surfaces 2a and 2b) of the substrate 2 are engraved with the
aforementioned linear grooves 2g and 2g' by dicing. A flat area
(plate-like portion 2c) to which the engraving of the grooves 2g
and 2g' does not extend is a support base for a ridge area formed
unengraved between the grooves 2g and 2g'.
[0063] The grooves 2g and 2g' of the substrate 2 are formed using a
rotary blade (with reference to the dicing blade J in FIG. 9) of a
dicing machine, and are spaced at predetermined intervals
(spacings) in one direction in surfaces to be machined (front
surface 2a and back surface 2b) of the substrate 2 so as to be
parallel to each other. Such machining on opposite sides is
performed in a manner to be described below. After the grooves 2g
are formed in one surface (for example, the front surface 2a), the
aforementioned substrate 2 is removed once from the dicing machine.
While being flipped upside down, the substrate 2 is attached to the
dicing machine. Then, the parallel linear grooves 2g' similar to
those in the aforementioned one surface (front surface 2a) are
formed in the other surface (back surface 2b) of the substrate 2,
with a phase difference of 90 degrees from the aforementioned one
surface (front surface 2a) side (in a direction orthogonal to the
grooves 2g on the front surface 2a side as seen in plan view).
[0064] It should be noted that the side surfaces (wall surfaces)
constituting the grooves 2g and 2g', which are formed by dicing
using the aforementioned rotary blade, are light-reflective
vertical surfaces (mirror surfaces), as in the aforementioned first
to third embodiments. Depending on the thickness of the
aforementioned blade J (total thickness between end surfaces), the
grooves 2g and 2g' obtained by engraving using the dicing blade J
have a groove width G of approximately 20 to 350 .mu.m and a groove
depth H of approximately 50 to 500 .mu.m, when the blade J having a
thickness of the order of 0.015 mm (15 .mu.m) to 0.3 mm (300 .mu.m)
is in general used. The remaining regions (ridge areas) where these
grooves 2g and 2g' are not formed are in the form of parallel ribs
having a width W of approximately 50 to 300 .mu.m and a height H of
approximately 50 to 500 .mu.m (the same as the depth of the
grooves).
[0065] When the aforementioned micromirror array 40 having the
aforementioned configuration is seen in the direction of the front
and back of the substrate (vertical direction), the grooves 2g on
the upper side (front surface 40a side) and the grooves 2g' on the
lower side (back surface 40b side) are orthogonal to each other in
the form of a lattice as seen in plan view. A corner reflector
[FIG. 8A] is formed at the intersection of each of the grooves 2g
and each of the grooves 2g'. Such a corner reflector includes a
light-reflective vertical surface (mirror surface) of each of the
grooves 2g on the front surface 40a side, and alight-reflective
vertical surface (mirror surface) of each of the grooves 2g' on the
back surface 40b side. In the micromirror array 40 according to the
fourth embodiment, light incident on one surface side of the
aforementioned array 40 is hence reflected once from the mirror
surface on the front surface 40a side, and is reflected once from
the mirror surface on the back surface 40b side. Then, the
reflected light is transmitted through the array 40 to the other
side thereof [FIG. 8B]. Thus, the micromirror array 40 according to
the present fourth embodiment is capable of forming a mirror image
of an object to be projected which is disposed on one surface side
of the array 40 at a spatial position on the other surface side
symmetrical to the object with respect to the plane of the array
40.
[0066] Also, in the aforementioned micromirror array 40, the
light-reflective vertical surfaces (mirror surfaces) at the corner
reflectors have a great aspect ratio [apparent virtual aspect
ratio; H/W; FIG. 8B]. Therefore, these light-reflective vertical
surfaces (mirror surfaces) are capable of projecting a bright and
sharp mirror image, as compared with conventional products.
[0067] Further, the aforementioned micromirror array 40, in which
the aforementioned grooves 2g and 2g' are formed in the front and
back surfaces of the single substrate 2, is characterized in that
the vertical distance between the mirror surfaces on the upper side
(front surface 40a side) and the mirror surfaces on the lower side
(back surface 40b side) is short, so that a relatively bright
mirror image is easily obtained. Also, the micromirror array 40 is
advantageous in that the array itself (total thickness) is made
thin, as compared with the micromirror arrays of other
embodiments.
[0068] Next, the manner of image formation of a mirror image in the
aforementioned embodiments will be described.
[0069] FIG. 8A is a plan view of corner reflector portions inside
the micromirror array according to the present invention as seen in
a vertical direction, and FIG. 8B is a schematic view showing a
three-dimensional structure of one corner reflector (a pair of
mirror surfaces of one corner reflector) thereof. In FIG. 8B, the
plate-like portions 1c and 1'c and the grooves 1g and 1'g of the
substrates 1 and 1' are not shown, based on the configuration of
the micromirror array 20 of the second embodiment (FIGS. 3 and 4)
formed by bringing the front surfaces 1a and 1'a with the grooves
1g and 1'g formed therein into abutment with each other as a
representative of the aforementioned embodiments. For ease of
viewing of the configuration of principal parts (the vertically
spaced mirror surfaces K1 and K2 of the corner reflector), FIG. 8B
schematically shows only an intersection portion of an upper ridge
area and a lower ridge area (a ridge area on the upper substrate 1'
side and a ridge area on the lower substrate 1 side) included among
the multiplicity of ridge areas (unmachined portions between the
grooves in the front surfaces 1a and 1' a) and disposed so that the
directions in which the grooves (ridges) extend are orthogonal to
each other as seen in plan view (three-dimensionally in "skew"
relation).
[0070] In the aforementioned other embodiments (first, third and
fourth), there are cases where the plate-like portions 1c, 1'c and
2c and the like of a substrate are held between these ridge areas
in the front surface 1'a on the upper side and the front surface 1a
on the lower side, so that the vertical distance between the
aforementioned mirror surfaces K1 and K2 is further increased.
However, the corner reflectors in these embodiments may be regarded
as those of the same configuration in principle, and are similar to
the above as seen in plan view, as shown in FIG. 8A.
[0071] Like the prior art shown in FIG. 14, when light incident on
one surface (front or back) side of the aforementioned micromirror
array 20 passes through the array, the incident light
(dash-double-dot lines) as seen in a vertical direction is
reflected once from each of the two mirror surfaces (K1 and K2) on
opposite sides of one corner (virtual corner portion) (twice in
total), as shown in FIG. 8A. The light reflected twice (passing
light) forms a mirror image (reversed image M') of an object M to
be projected at a spatial position on the other surface side of the
aforementioned array (position symmetrical to the object M with
respect to the plane of the element surface).
[0072] When this is viewed three-dimensionally, one light
reflecting surface [virtual region formed in an inner wall surface
(mirror surface) of the ridge in the front surface 1a on the lower
side; K1] and the other light reflecting surface [virtual region
formed in an inner wall surface (mirror surface) of the ridge in
the front surface 1'a on the upper side; K2] of each unit optical
element are disposed in vertically spaced apart relation (in "skew"
relation) in the micromirror array 20 according to the present
invention, as shown in FIG. 8B. Thus, light (dash-double-dot lines)
traveling through one surface (in the figure, the lower surface
closer to the object M to be projected) of the aforementioned array
into the ridge in the front surface 1a on the lower side is
reflected once from the aforementioned lower mirror surface
(region) K1, and is subsequently reflected a second time from the
mirror surface (region) K2 in the ridge in the front surface 1'a on
the upper side which the light has entered. Thereafter, the light
travels out of the other surface (the upper surface closer to the
reversed image M') of the aforementioned array in a direction
symmetrical with respect to the plane of the element surface
(abutment surface T of the aforementioned ridges in the front
surfaces 1a and 1'a) [with reference to FIG. 8B and FIG. 14].
[0073] For the micromirror array employing the aforementioned
manner of image formation of a mirror image, the brightness and
sharpness of the mirror image (reversed image M') thereof is
considered to be proportional to the amount of light passing
(transmitted) through the aforementioned element surface (abutment
surface T of the aforementioned ridges in the front surfaces 1a and
1'a). Specifically, the amount of light (passing light amount)
passing through the element surface by being reflected twice in the
aforementioned array is considered to depend on the size (effective
area) and light reflectivity of the mirror surfaces (regions) K1
and K2 adjacent to the aforementioned element surface T. In
particular, when light reflection from a reflecting surface
(interface between a mirror surface and air space) is total
reflection, the passing light amount is considered to be
proportional to the areas of the mirror surfaces (regions) K1 and
K2 (=apparent "virtual aspect ratio" of the aforementioned mirror
surfaces).
[0074] According to a method of manufacturing a micromirror array
according to the present invention to be described later, the
aforementioned micromirror array is high in design flexibility to
achieve the formation of a unit optical element of a desired shape
[groove width G, spacing between grooves (groove intervals=width W
of ridge portions), and groove depth (height H of ridge portions)]
by means of the dicing blade J. Thus, the micromirror array and the
optical elements constituting the micromirror array according to
the present invention are capable of increasing the apparent
effective area and virtual aspect ratio [the ratio of height H
(length in the thickness direction of the substrate) to width W
(width of ridge portions in the horizontal direction of the
substrates) in the virtual region=H/W; with reference to FIG. 8B]
of the light-reflective vertical surfaces (vertically spaced mirror
surfaces K1 and K2) constituting the corner reflectors, as compared
with conventional products. This achieves the projection of a
bright, high-luminance and sharp mirror image.
[0075] The preferred shape of the grooves (for example, 1g, 1'g, 2g
and 2g') obtained by engraving using the aforementioned dicing
blade J includes a groove width G of approximately 20 to 350 .mu.m
and a groove depth H of approximately 50 to 500 .mu.m, as mentioned
earlier. The preferred shape of the thereby obtained remaining
regions (ridge portions) where the aforementioned grooves are not
formed includes a width W of approximately 50 to 300 .mu.m in the
horizontal direction of the substrate, and a height H of
approximately 50 to 500 .mu.m (the same as the depth of the
grooves) in the thickness direction of the substrate. When the
aforementioned array (substrate) is seen in plan view, it is
desirable that the "ratio (W/G) of the width W of the ridge
portions to the groove width G" is preferably not less than 1.0,
and more preferably not less than 3.0 (the same applies to the
optical element unit). In this case, the spacings between the
grooves are represented by "G+H".
[0076] It is desirable that the ideal shape of the light reflecting
surfaces (virtual regions K1 and K2 on the mirror surfaces) of the
unit optical elements (corner reflectors) which is produced by
stacking the aforementioned substrates (ridge portions) one on top
of the other is such that the "virtual aspect ratio (H/W)" thereof
is preferably not less than 1.0, and more preferably not less than
3.0 [with reference to FIG. 8B].
[0077] Next, a method of manufacturing a micromirror array and
optical elements for use in the micromirror array according to the
aforementioned embodiments will be described.
[0078] FIG. 9 is a schematic view of the configuration of a dicing
machine for use in the manufacturing method for a micromirror array
according to the embodiments of the present invention. In the
figure, the reference character J designates a dicing blade (rotary
blade), S designates a movable stage for machining, and W
designates a substrate (workpiece) to be machined.
[0079] The manufacture of the micromirror array 10 according to the
aforementioned first embodiment is as follows. First, a transparent
flat substrate 1 is prepared. This substrate is attached as a
workpiece W at a predetermined position of the machining stage
(movable stage S) of the dicing machine (with reference to FIG. 9).
The linear grooves 1g and 1'g parallel to each other are
sequentially formed at predetermined intervals in a surface (one
surface) of the aforementioned substrate by using the rotary blade
(dicing blade J). Next, two substrates (optical elements) with the
aforementioned linear grooves formed therein are used so that the
front surface 1a of the first substrate 1 and the back surface 1'b
of the second substrate 1' are joined together. The substrates 1
and 1' are stacked together so that the continuous directions in
which the linear grooves 1g and 1'g of the substrates 1 and 1'
extend are orthogonal to each other as seen in plan view, to
thereby constitute a single unit. This will be described step by
step below.
[0080] The manufacture of the micromirror array 10 by the use of
the aforementioned dicing machine (dicing saw) is as follows.
First, a flat substrate made of a material having a visible light
transmittance of not less than 80%, e.g. acrylic resin and the
like, is prepared as a substrate (workpiece W) to be machined into
the array 10 [substrate preparing step].
[0081] Next, this substrate is affixed at a predetermined position
on the aforementioned movable stage S with an adhesive tape, a
gluing agent or the like, as shown in FIG. 9, with the surface to
be machined facing upward (on the blade J side), and is attached
and fixed (temporarily fixed) thereto as the workpiece W. The
workpiece W may be grasped with a chuck, a vise and the like
without using the gluing agent and the like [workpiece attaching
step].
[0082] Next, the aforementioned movable stage S is moved to a
machining start position. While being rotated at a high speed, the
aforementioned blade J is moved downwardly to a position at which
the aforementioned workpiece W is engravable. In accordance with a
previously programmed procedure, the aforementioned workpiece W
(movable stage S) is slid horizontally (in the x-axis direction),
so that the surface to be machined (front surface) of the workpiece
W is engraved with a linear groove having a desired depth (50 to
500 .mu.m).
[0083] After the engraving process for one linear groove is
completed, the aforementioned movable stage S is moved to a
machining start position for the next groove. Then, the
aforementioned workpiece W is slid horizontally (in the x-axis
direction) at a predetermined feed speed again, so that the
aforementioned next groove is formed by machining. The engraving of
such a linear groove is repeated at predetermined intervals
(spacings) in one direction (in the y-axis direction), the
plurality of linear grooves 1g and 1'g arranged in a predetermined
direction (y direction at this time) and parallel to each other are
formed [groove forming step].
[0084] The aforementioned dicing machine will be described in
further detail. The machine (with reference to FIG. 9) for use in
this manufacturing method is referred to as a dicing machine, a
dicing saw or the like. The dicing machine includes a rotary blade
(diamond blade such as the dicing blade J) attached to the tip of a
spindle (not shown) rotating at a high speed, a machining stage
(movable stage S) for placing and temporarily fixing thereon a
substrate (workpiece W) formed into a micromirror array after
machining, a stage driving means for moving this movable stage S in
three axis (x, y and z) directions corresponding to the rotation,
and upward and downward movements of the aforementioned blade J and
for rotating the movable stage S about the z axis (6).
[0085] The aforementioned dicing blade J is a substantially
ring-shaped ultrathin peripheral cutting edge, and has
small-diameter abrasive grains of industrial diamond added to a
cutting part provided on the outer peripheral surface (and also to
left-hand and right-hand side end surfaces in some cases) thereof.
The thickness (total thickness in the direction of end surfaces) of
the blade J used herein is on the order of 0.015 mm (15 .mu.m) to
0.3 mm (300 .mu.m), and the width of the grooves 1g and 1'g
obtained by engraving using this blade J is on the order of 0.02 mm
to 0.35 mm. Although the blade J used herein has a flat outer
peripheral surface (cutting edge surface), a blade having the
aforementioned cutting edge surface of a triangular, circular and
oval cross-sectional shape may be used.
[0086] As shown in FIG. 9, the movable stage S for temporarily
fixing the aforementioned workpiece W is provided on a slider
(linear motion bearing) capable of freely moving (positioning) the
position thereof in at least two, i.e. x and y, directions. In this
example, the movable stage S is further capable of moving up and
down in the z-axis direction (not shown) and rotating about the x
axis (6). The stage driving means in each axial direction (about
each axis), which is similar in mechanism to a general-purpose
machine tool, will not be described, but is capable of intermittent
operation of the movable stage S, precise position control thereof,
and programmed constant-speed travel thereof by means of a stepping
motor, an actuator and the like. Some dicing machines are designed
such that combinations of the spindles and the blade J are disposed
in positions far from or close to each other so as to form a
plurality of parallel grooves at a time by engraving.
[0087] With the position of the aforementioned movable stage S
fixed, the positions of the spindle and the blade J may be moved
and rotated horizontally to form a linear groove similar to that
described above by engraving. The grain size of the abrasive grains
of diamond used for the dicing blade J is generally on the order of
#240 to #5000. In consideration of surface roughening of the light
reflecting surfaces (opposite side walls of the grooves) after the
dicing (although the mirror surfaces are desirable), it is
preferable that the grain size of the abrasive grains is not less
than #1000.
[0088] Next, after the completion of the engraving of the surface
to be machined of the aforementioned workpiece W with a previously
determined number of grooves, the workpiece W is removed from over
the movable stage S, and a new workpiece W is set thereon. The
groove engraving is repeated to form the linear grooves of the same
shape and of the same pattern are formed in a plurality of
workpieces W (substrates).
[0089] Next, two substrates (optical elements) with the
aforementioned linear grooves formed therein are used. The front
surface 1a of the first substrate 1 and the back surface 1'b of the
second substrate 1' are joined together. The substrates 1 and 1'
are stacked together so that the directions in which the linear
grooves 1g and 1'g of the substrates 1 and 1' extend are orthogonal
to each other as seen in plan view [the aforementioned manner of
stacking (D)]. While being stacked together, these substrates 1 and
1' are fixed together with an adhesive agent, a double-sided
adhesive tape and the like, to thereby constitute an integral
(single) unit. This provides the micromirror array 10 of the first
embodiment [substrate stacking step].
[0090] A method for fixing the aforementioned substrates 1 and 1'
includes the use of a vise, a case (housing) or the like which
inserts the aforementioned array 10 thereinto or surrounds the
aforementioned array 10 to fix the substrates 1 and 1' in addition
to the use of a member, an agent and the like, such as the
aforementioned adhesive agent or the double-sided adhesive tape,
which is put between the substrates to fix the substrates. If
slight misregistration occurs at the stacking position (horizontal
position) of the substrates 1 and 1' constituting the
aforementioned micromirror array 10, the optical performance of the
corner reflectors appearing at the intersection portions of the
upper grooves 1g and the lower grooves 1'g is maintained. Thus, the
fixing may be loose enough to prevent the misregistration at these
positions.
[0091] The manufacturing method for a micromirror array according
to the aforementioned first embodiment is capable of forming the
aforementioned linear grooves 1g and 1'g with high accuracy and
with high efficiency. Also, the aforementioned manufacturing method
for a micromirror array does not include any step which damages the
array as in a molding method and the like, to thereby improve the
efficiency (yield) of the array manufacture. Therefore, the
manufacturing method for a micromirror array according to the
present invention is capable of manufacturing a micromirror array
easily at low costs, as compared with conventional manufacturing
methods.
[0092] Next, a method of manufacturing the micromirror array 20
according to the aforementioned second embodiment will be
described. The manufacturing method for the micromirror array 20
according to the second embodiment differs from the manufacturing
method for the micromirror array 10 according to the aforementioned
first embodiment in the step of stacking the substrates 1 and 1'
together (the manner of stacking). This step will be principally
described.
[0093] The manufacture of the micromirror array 20 according to the
aforementioned second embodiment is as follows. As in the
manufacturing method of the aforementioned first embodiment, a
transparent flat substrate (optical element) is initially prepared.
This substrate is attached as a workpiece W at a predetermined
position of the machining stage (movable stage S) of the dicing
machine (with reference to FIG. 9). The linear grooves 1g and 1'g
parallel to each other are sequentially formed at predetermined
intervals in one surface of the aforementioned substrate by using
the rotary blade (dicing blade J).
[0094] Next, two substrates 1 and 1' with the aforementioned linear
grooves formed therein are used. With the first upper substrate 1'
flipped upside down and rotated 90 degrees horizontally relative to
the second lower substrate 1, the front surface 1' a where the
grooves 1'g are formed in the upper substrate 1' (the lower surface
of the plate-like portion 1'c) is brought into abutment with the
front surface 1a where the grooves 1g are formed in the lower
substrate 1, as shown in FIG. 4. These substrates 1 and 1' are
stacked together so that the directions in which the grooves 1g and
the grooves 1'g provided in the substrates 1 and 1' extend are
orthogonal to each other as seen in plan view [the aforementioned
manner of stacking (E)]. While being stacked together, these
substrates 1 and 1' are fixed together with an adhesive agent, a
double-sided adhesive tape and the like, to thereby constitute an
integral (single) unit. This provides the micromirror array 20 of
the second embodiment.
[0095] A method for fixing the aforementioned substrates 1 and 1'
includes the use of a vise, a case (housing) or the like which
inserts the aforementioned array 20 thereinto or surrounds the
aforementioned array 20 to fix the substrates 1 and 1' in addition
to the use of a member, an agent and the like, such as the
aforementioned adhesive agent or the double-sided adhesive tape,
which is put between the substrates to fix the substrates, as in
the aforementioned first embodiment. In the micromirror array 20 of
the second embodiment in which the stacking is performed in the
manner (B) and in the manner of stacking (E), the grooves 1g and
1'g of the substrates 1 and 1' face inward after the stacking. This
is advantageous in that there is a low likelihood that foreign
matter, such as grit and dust, which hinders light reflection comes
into these grooves 1g and 1'g, so that light reflection performance
decreases slightly with time.
[0096] For the manufacture of the micromirror array 30 of the
aforementioned third embodiment, the array 30 is produced in a
manner similar to that described above. However, when the
substrates 1 and 1' are finally stacked together, the substrate 1'
flipped upside down is disposed under the substrate 1. Then, with
the substrate 1' rotated 90 degrees relative to the second upper
substrate 1, the back surface 1b of the upper substrate 1 (the
lower surface of the plate-like portion 1c) is brought into
abutment with the back surface 1'b of the lower substrate 1' (the
upper surface of the plate-like portion 1'c). The substrates 1 and
1' are stacked together so that the directions in which the grooves
1g and the grooves 1'g provided in the substrates 1 and 1' extend
are orthogonal to each other as seen in plan view [the
aforementioned manner of stacking (F)].
[0097] The manufacturing methods for a micromirror array according
to the aforementioned second and third embodiments are capable of
forming the aforementioned linear grooves 1g and 1'g with high
accuracy and with high efficiency, as in the first embodiment.
Also, the aforementioned manufacturing methods for a micromirror
array do not include any step which damages the array as in a
molding method and the like, to thereby improve the efficiency
(yield) of the array manufacture.
[0098] Next, a method of manufacturing the micromirror array 40
according to the aforementioned fourth embodiment will be
described. It should be noted that a dicing machine for use in the
manufacturing method for the micromirror array 40 according to the
fourth embodiment is similar in structure to the machine described
above, and will not be described in detail.
[0099] The manufacture of the micromirror array 40 according to the
aforementioned fourth embodiment is as follows. First, a
transparent flat substrate 2 is prepared. This substrate is
attached as a workpiece W at a predetermined position of the
machining stage (movable stage S) of the dicing machine (with
reference to FIG. 9). The linear grooves 2g and 2g' parallel to
each other are sequentially formed at predetermined intervals in
one surface (surface to be machined) of the aforementioned
substrate by using the rotary blade (dicing blade J).
[0100] Next, this substrate (workpiece W) is removed once from the
aforementioned machining stage S, and is flipped upside down. This
substrate is attached again as a workpiece W at a predetermined
position of the machining stage S, with the back surface (surface
to be machined) of the aforementioned substrate facing upward. The
linear grooves 2g and 2g' parallel to each other and extending in a
direction orthogonal to the linear grooves formed in the
aforementioned front surface are sequentially formed at
predetermined intervals in the back surface by using the
aforementioned dicing blade J. This achieves the production of the
micromirror array 40 in which the grooves 2g formed on the front
surface 40a side and the grooves 2g' formed on the back surface 40b
are orthogonal to each other in the form of a lattice as seen in
plan view, when seen in the direction of the front and back of the
substrate (vertical direction), as shown in FIG. 7.
[0101] The manufacturing method for a micromirror array according
to the aforementioned fourth embodiment is also capable of forming
the aforementioned linear grooves 2g and 2g' with high accuracy and
with high efficiency, as in the first to third embodiments. Also,
this method does not include any step which damages the array as in
a molding method and the like, to thereby improve the efficiency
(yield) of the array manufacture.
EXAMPLES
[0102] Next, examples in which the micromirror arrays of the
aforementioned first to fourth embodiments are produced will be
described. It should be noted that the present invention is not
limited to the examples to be described below.
Example 1
[0103] First, an acrylic board serving as a substrate was prepared,
and the micromirror array of the first embodiment was produced by
dicing.
<Acrylic Board>
[0104] A substrate made of acrylic resin (flat board): 50
mm.times.50 mm.times.2 mm in thickness.
<Dicing Machine>
[0105] Automatic dicing saw DAD3350 manufactured by Disco
Corporation.
<Dicing Conditions>
[0106] Dicing blade <NBC-Z2050 manufactured by Disco
Corporation> with a blade thickness of 25 .mu.m. [0107] Spindle
rpm: 30000 rpm. [0108] Table feed speed: 3.0 mm/sec. [0109]
Cooling: shower cooler (water) 1 L/min, and shower nozzle (water)
0.5 L/min.
[0110] <Production of Optical Elements>
[0111] The aforementioned acrylic board was affixed to an adhesive
tape <dicing tape: ELEP manufactured by Nitto Denko
Corporation> and fixed thereto. In that state, the resultant
structure obtained by fixing the aforementioned acrylic board was
set on a chuck table (machining stage) of the dicing machine
<manufactured by Disco Corporation>. Then, a predetermined
number of grooves having a width of 30 .mu.m and a depth of 300
.mu.m were engraved (dug) at intervals (spacings) of 100 .mu.m in a
surface to be machined (upper surface) of the aforementioned
acrylic board under conditions shown in <Dicing Conditions>
described above so as to be parallel to each other. Thus, an
optical element serving as a unit of manufacture was produced, as
shown in FIGS. 2, 4 and 6. It should be noted that a plurality of
optical elements are produced.
[0112] Two optical elements obtained as described above were used.
With a first upper one of the optical elements (substrates) rotated
90 degrees horizontally relative to a second lower one of the
optical elements (substrates) as shown in FIG. 2, the back surface
(lower surface) of the upper optical element was brought into
abutment with the front surface (upper surface) of the lower
optical element. Then, the two optical elements were stacked
together [aforementioned configurations (A) and (D)]. An adhesive
agent <Acrysunday adhesive agent manufactured by Acrysunday Co.,
Ltd.> in small amounts was used for bonding and fixing at four
corners of the array. Thus, the micromirror array of Example 1 was
produced (with reference to FIG. 1).
Example 2
[0113] Two optical elements obtained as described above were used.
With a first upper one of the optical elements (substrates) flipped
upside down and rotated 90 degrees horizontally relative to a
second lower one of the optical elements (substrates) as shown in
FIG. 4, the front surface (lower surface) of the upper optical
element was brought into abutment with the front surface (upper
surface) of the lower optical element. Then, the two optical
elements were stacked together [aforementioned configurations (B)
and (E)]. An adhesive agent <Acrysunday adhesive agent
manufactured by Acrysunday Co., Ltd.> in small amounts was used
for bonding and fixing at four corners of the array. Thus, the
micromirror array of Example 2 was produced (with reference to FIG.
3).
Example 3
[0114] Two optical elements obtained as described above were used.
With a first lower one of the optical elements (substrates) flipped
upside down and rotated 90 degrees horizontally relative to a
second upper one of the optical elements (substrates) as shown in
FIG. 6, the back surface (lower surface) of the upper optical
element was brought into abutment with the back surface (upper
surface) of the lower optical element. Then, the two optical
elements were stacked together [aforementioned configurations (C)
and (F)]. An adhesive agent <Acrysunday adhesive agent
manufactured by Acrysunday Co., Ltd.> in small amounts was used
for bonding and fixing at four corners of the array. Thus, the
micromirror array of Example 3 was produced (with reference to FIG.
5).
Example 4
[0115] First, an acrylic board serving as a substrate was prepared,
and an optical element similar to those used in Examples 1 to 3 [an
acrylic board in which a plurality of parallel grooves are formed
by engraving in one surface (front surface) thereof] was produced
by dicing. Next, this acrylic board was removed once from the
machining stage. After being flipped upside down and rotated 90
degrees, the acrylic board was attached again onto this machining
stage with the aforementioned adhesive tape, with the back surface
(a second surface to be machined) of the aforementioned acrylic
board facing upward. Then, a predetermined number of linear grooves
similar in shape to the grooves (having a width of 30 .mu.m and a
depth of 300 .mu.m at intervals of 100 .mu.m) formed on the
aforementioned front surface side were engraved (dug) in the second
surface to be machined (upper surface) of the aforementioned
acrylic board under conditions shown in <Dicing Conditions>
described above so as to extend in a direction orthogonal to the
linear grooves formed on the front surface side. Thus, the
micromirror array of Example 4 was produced as shown in FIG. 7.
[0116] The micromirror array L obtained in each of Examples 1 to 4
was set horizontally. A liquid crystal display panel (LCD) was
disposed at an inclined angle of 45 degrees at a position lying
under the micromirror array L, as shown in FIG. 10. Then, an
evaluation image (a white square measuring 1 cm.times.1 cm) of a
predetermined luminance was displayed on the aforementioned LCD. As
a result, a mirror image (indicated by a dotted line in the figure)
of the aforementioned evaluation image was image-formed at a
spatial position symmetrical to the evaluation image with respect
to the plane of an element surface P when any one of the
micromirror arrays L of Examples 1 to 4 was used. From this fact,
it is found that each of the micromirror arrays of the
aforementioned examples functions as an image-forming optical
element.
[0117] Next, the groove depth and the height H of ridge portions of
each optical element (substrate) constituting the micromirror
arrays of the present invention were changed, so that micromirror
arrays (Examples 5 to 10) were produced which were different in
"the ratio of height H (length in the thickness direction of the
substrates) to width W (width of ridge portions in the horizontal
direction of the substrates)" [aspect ratio (H/W)] of light
reflecting surfaces [virtual regions K1 and K2; with reference to
FIG. 8B] of the micromirror arrays and in effective light
reflection area. Using these micromirror arrays, comparisons of the
"brightness (luminance)" of mirror images (spatial images) and the
"sharpness (visual recognizability)" of the images were made in the
case where a predetermined image displayed on a liquid crystal
display (LCD) was projected by a method similar to that (FIG. 10)
of "Example 1" described above.
[0118] It should be noted that <Dicing Conditions> used
herein for the acrylic board were similar to processing condition
of "Example 1" described above. The dimensions of the produced
micromirror arrays were observed and measured with a microscope
<VHX-200 manufactured by Keyence Corporation> and a laser
microscope <VK-9700 manufactured by Keyence Corporation>.
Because the same dicing blade is used in Examples 5 to 10 described
above, all of the examples have the same groove width G (30 .mu.m),
the same width W (70 .mu.m) of ridge portions, and the same
spacings between grooves (G+H) except for the aforementioned groove
depth (height H of ridge portions).
[0119] The aforementioned micromirror array includes two optical
elements identical in specs with each other, as shown in FIG. 4.
The front surface 1'a where the grooves 1'g are formed in the first
substrate 1' is brought into abutment with the front surface 1a
where the grooves 1g are formed in the second substrate 1. These
substrates 1 and 1' are stacked one on top of the other so that the
directions in which the grooves 1g and the grooves 1'g provided in
the substrates 1 and 1' extend are orthogonal to each other as seen
in plan view, to constitute the single micromirror array as shown
in FIG. 3 [aforementioned configurations (B) and (E)].
[0120] [Brightness Measurement of Mirror Image (Spatial Image)]
[0121] The micromirror array L obtained in each of Examples 5 to 10
was set horizontally, as shown in FIG. 10, and the LCD was disposed
at an inclined angle of 45 degrees at a predetermined position
lying under the micromirror array L. Then, an evaluation image (a
white square measuring 1 cm.times.1 cm) of a predetermined
luminance was displayed on the aforementioned LCD. The brightness
(luminance) of a mirror image (indicated by a dotted line in the
figure) projected at a spatial position symmetrical to the
evaluation image with respect to the plane of the element surface P
was measured from above at a distance of 50 cm from the mirror
image at a downward angle of 45 degrees in opposed relation to the
mirror image. The measurement of the brightness of the
aforementioned mirror image was made in a darkroom. A luminance
meter Q <BM-9 manufactured by Topcon Corporation> was used
for the measurement of the brightness of the mirror image.
[0122] [Evaluation of Visual Recognizability of Mirror Image
(Character)]
[0123] Following the aforementioned "Brightness Measurement of
Mirror Image", an evaluation image (black Kanji characters for
"Nitto Denko" in Ming-style type (Mincho typeface) each measuring 2
cm.times.2 cm on a white background) of a predetermined luminance
was displayed on the aforementioned LCD by using a similar
arrangement (with reference to FIG. 10). A mirror image (indicated
by the dotted line in the figure) projected at the spatial position
symmetrical to the evaluation image with respect to the plane of
the element surface P was visually observed from above at a
distance of 50 cm from the mirror image at a downward angle of 45
degrees in opposed relation to the mirror image. The evaluation of
the visual recognizability of the aforementioned mirror image was
performed under a fluorescent light (300 lux or more) in a room.
The evaluation was as follows: a mirror image in which even the
details of the characters were clearly visually recognizable was
indicated by "S"; a mirror image which was visually recognizable as
characters but not clear was indicated by "A"; and a mirror image
which was not visually recognizable as characters was indicated by
"F".
[0124] The results of the aforementioned measurement are shown in
"Table 1" below.
TABLE-US-00001 TABLE 1 Ex. Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 10 Width G
of 30 30 30 30 30 30 Grooves between Ridges (.mu.m) Width W of
Light 70 70 70 70 70 70 Reflecting Surfaces (Unit Optical Elements)
(.mu.m) Height H of Light 70 146 217 286 354 430 Reflecting
Surfaces (Unit Optical Elements) (.mu.m) Aspect Ratio 1.00 2.09
3.10 4.09 5.06 6.14 (H/W) Brightness 0.11 0.24 0.44 0.65 0.77 0.59
(Luminance) (cd/m.sup.2) Visual A A S S S S Recognizability
(Character Image)
[0125] The aforementioned results of "brightness (luminance)" in
"Table 1" showed that the higher the virtual aspect ratio (H/W) of
the light reflecting surfaces (Example 5.fwdarw.Example 9), the
more improved the brightness (luminance) of the aforementioned
mirror image. In Examples 5 and 6 in which the aforementioned
luminance was less than 0.4 cd/m.sup.2, the characters in the image
were difficult to recognize. In Examples 7 and 10 in which the
aforementioned luminance was not less than 0.4 cd/m.sup.2, the
characters were in a clearly legible condition.
[0126] Examples of how the actual characters (mirror image) look
like in Examples 7 to 10 which show successful results of the
aforementioned "Visual Recognizability of Mirror Image (Character)"
are shown as reference photographs in FIG. 11. The visual
recognizability of character images is dependent on the ambient
environment (brightness) and resolution, and hence cannot be
defined unconditionally. It was, however, found from the
aforementioned results of the reference photographs that the
luminance (absolute value) of the mirror image (projected image)
was preferably not less than 0.4 cd/m.sup.2, and further desirably
not less than 0.5 cd/m.sup.2.
[0127] In the aforementioned examples, the test was conducted using
the micromirror array configured by bringing the front surfaces (1a
and 1'a) where the grooves 1'g were formed in the two optical
elements identical in specs with each other into abutment with each
other [with reference to FIG. 3; aforementioned configuration (B)].
However, substantially similar results were obtained when the test
was conducted using the micromirror array configured by bringing
the back surfaces (1b and 1'b) where the grooves 1'g were not
formed into abutment with each other [with reference to FIG. 5;
aforementioned configuration (C)].
[0128] Although specific forms in the present invention have been
described in the aforementioned examples, the aforementioned
examples should be considered as merely illustrative and not
restrictive. It is contemplated that various modifications evident
to those skilled in the art could be made without departing from
the scope of the present invention.
[0129] The micromirror array, the manufacturing method for the
micromirror array, and optical elements for use in the micromirror
array according to the present invention are capable of
manufacturing a micromirror array which forms a bright
high-luminance image with high efficiency. The manufacturing method
for the micromirror array according to the present invention
contributes to the reduction in costs thereof.
REFERENCE SIGNS LIST
[0130] 1, 1' Substrates [0131] 1a, 1'a Front surfaces [0132] 1b,
1'b Back surfaces [0133] 1c, 1'c Plate-like portions [0134] 1g, 1'g
Grooves [0135] 2 Substrate [0136] 2a Front surface [0137] 2b Back
surface [0138] 2g, 2g' Grooves [0139] 3, 4 Substrates [0140] 10,
20, 30, 40 Micromirror arrays [0141] 10a, 20a, 30a, 40a Front
surfaces [0142] 10b, 20b, 30b, 40b Back surfaces [0143] 50
Micromirror array [0144] 51 Minute holes [0145] 60 Micromirror
array [0146] 61 Minute protruding portions [0147] K Corners [0148]
K1, K2 Mirror surfaces [0149] L Micromirror array [0150] M Object
to be projected [0151] M' Reversed image [0152] P Element surface
[0153] Q Luminance meter [0154] J Blade [0155] S Movable stage
[0156] W Workpiece
* * * * *